This invention relates to a method and apparatus for sewing cover halves on a ball core. More specifically, the invention comprises a method and apparatus for stitching elliptical lemniscate halves of a ball cover around a core.
The construction of softballs, baseballs, and the like, as established by regulation and tradition, comprises the formation of a spherical foundation which is then wrapped with a continuous random overlay of elastic strand to form a ball core. The external dimensions of the ball core are maintained uniformly within narrow tolerances. A leather covering is then applied to the core in the general configuration of two bilobate pieces fitted about the ball core with the interconnecting section of one piece disposed in a posture with its edges abutting the lobes of the other half.
Traditionally stitching is provided to fasten the edges of the cover halves together and to draw them uniformly and neatly into abutment. The exposed threads of the stitching forms a seam of herringbone configuration centered along the line of abutment of the cover edges. More specifically each exposed thread of the seam passes over and under an opposite abutting edge of a cover place. Moreover each thread is doubled to provide greater strength without additional thickness. By this stitching technique the edges of the cover pieces or halves are drawn snugly against each other to provide a spherical close fitting cover without exposure of the core or the edges of the cover halves. This results in a comparatively smooth and uniform ball.
Initially the stitching of baseballs and the like was performed by a hand operation. Hand stitching, however, is highly labor intensive and rapidly was targeted as one of the most expensive and time consuming aspects of the ball manufacturing operation.
Various elements in the industry theorized that machine sewing baseballs and the like would be desirable and it is believed that others have tried extensively to achieve a mechanized method and apparatus which would be capable of performing a ball stitching or sewing operation. The ball industry in general, and particularly the baseball industry and major leagues, however, have demanding regulations and standards which previously known ball stitching machines have been unable to meet. In this connection baseballs and the like require a double herringbone stitch with the "V" or vertex of the stitch directly over the seam line. The thread pairs must be uniform and regular without twisting of adjacent threads. The ball cover halves must be stretched tightly over the ball core and no space between the abutting edges of the cover halves along the seams is permitted. Additionally the stitch holes must be sharply defined without evidence of any pulling or tearing or other leather surface damage. Moreover the leather surface of the cover halves must be free of any grease, oil or any other residue which might impair the playability of the end product.
The foregoing stitch pattern, uniformity and quality requirements for official baseballs and the like have rendered previously known machines unacceptable and useless to the industry. As a consequence, it is believed that all major league baseballs are presently hand sewn in a labor intensive manner which has been known for decades.